Marie Lu doesn't disappoint in writing action-packed thrillers...
Spies? Missions? Near-death experiences?

Progress:
It's a bit like a YA version of Mission Impossible.
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It begins so damn slowly that made me consider DNF-ing it, but Marie Lu's books have, so far been fun to read, so I decided to go for it. Alas, it took me a month to actually continue the book.
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Eventually, this book got so, so much better...
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TBH, it would have been better if the author had shortened the first nine chapters as much as possible because the rest is absolutely mind-boggling and so fun!
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The ending was a bit boring. It wasn't enough to carry the entire novel. I'd have loved if it was left open-ended.
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Post-read:
Character development wasn't exactly "great" per se, neither the chemistry between the characters. The romance was very superficial.
The dialogues felt so juvenile and mediocre, if their age wasn’t mentioned I’d guess that it’s around 14-16 y/o.
The writing was unbearably descriptive, especially, with lots of flashbacks, thus overshadowing the action scenes.
This book lacked a significant amount of its world-building and plot, as compared to the other two series I've read of this author's —Warcross duology and Legend Trilogy .
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Overall, it was fun, somewhat okay and a light action-packed novel.
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Stunning covers by the way!